Method of deactivating sponge iron



United States Patent Ofifice 2,766,108 Patented Oct. 9, 1956 John E.Eberhardt, Bethlehem, Hugh S. Graham, Hellertown, and Richard G. Gold,Coopersburg, Pa., assignors to Bethlehem Steel Company, a corporation ofPennsylvania No Drawing. Application June 30, 1955, Serial No. 519,258

8 Claims. (Cl. 75--.5)

This invention relates to improvements in the deactivation of spongeiron and particularly to the deactivation of compacted sponge iron.

By sponge iron, as is well known, is meant metallic iron which has beenchemically reduced from its oxide without fusion. The particular spongeiron with which this invention is concerned is sponge iron which hasbeen compressed or compacted into solid pieces which are better adaptedfor use in certain metallurgical processes than the powdered form ofsponge iron.

In a process of producing sponge iron which is at present beingpracticed, finely divided iron ore is treated with hydrogen or otherreducing gas by means of the well known fiuidization process in a heatedreactor. The reduced iron which leaves the reactor in powder form is,while still in a protective atmosphere to prevent oxidation, fed betweenrolls which compress or compact the iron into a continuous strip,preferably about one-quarter inch in thickness. This strip then passesthrough a breaker, which breaks the material into fragments or chips ofa usable size, say in the neighborhood of two by three inches.

One fiaw in this process, as heretofore known, however, was that thecompacted material could not be stored to await further use. It wasfound that when the chips were stored in piles, the underneath layers ofchips commenced to reoxidize, and this reoxidation continued until thematerial had reverted practically to the state of oxidation in which itwas prior to the reducing treatment. In this state the material couldnot be put to its intended use.

We have discovered a method of treating the sponge iron chips which putsthem in a condition allowing them to be stored in piles for anindefinite time without occur rence of reoxidation. This method consistsprimarily in allowing a slight, initial oxidation of the chips to takeplace, and meanwhile subjecting them to a draft of cooling air. Thiscooling step arrests the oxidation before the chips have heated up morethan about 300 to 400 degrees F., and thereafter further oxidation doesnot occur. The slight initial oxidation that has taken place does notaffect the utility of the material.

In the practice of our invention, the sponge iron chips are dischargedfrom the compacting apparatus into the atmosphere. At this point thechips are at a temperature of from 100 F. to 400 F. The chips areimmediately delivered to an apparatus which is capable of subjectingthem to a gentle tumbling action. For example, the chips may be fed intoa rotating drum, or they may be fed onto the first step of a clinkercooler such as is well known in the cement industry and which slowlypushes the material forward and down over a series of steps, tumblingthe chips a number of times during their travel to the end of thecooler.

If the chips are treated in a drum, a continuous stream of air will beblown through the drum, subjecting all surfaces of the chips to theoxidizing and cooling action of the air.

Ona clinker cooler, the bed of the cooler may be perfQrated and air bedrawn down through the perforations, oxidizing and cooling the chips inthe process.

Whichever apparatus is used, the air is blown over the chips at avelocity snificient to arrest the oxidation of the chips before theirtemperature has risen by more than three or four hundred degrees abovewhat it was at the beginning of the cooling step.

As an example of what we have done, we have treated chips of iron madeby reducing Swedish ore on a clinker cooler, the area of the bed ofwhich was approximately 36 square feet. Air was blown past the chips onthe cooler at a rate of approximately 5,000 C. F. M. and the timerequired for the chips to travel the length of the cooler was about 11to 13 minutes. A slight initial oxidation of the chips occurred, causinga rise in their temperature of to 300 degrees F., after which oxidationceased and their temperature dropped, eventually reach ing nearlyatmospheric temperature before they were discharged from the clinkercooler. The material was then stored in piles, and no further oxidationtook place.

We are not aware of the exact reason for the effect our treatment has onthe sponge iron chips. It may be that the very thin and harmless film ofoxide formed on the chips renders them impervious to further oxidation.Whatever the explanation, our treatment has made it possible to storefor indefinite periods material which heretofore could not be storedwithout reoxidizing.

The term deactivating" or deactivation as used in the following claimsmeans the treatment of the material in question to render itnon-oxidizable in air at atmospheric temperatures.

We claim:

1. A method of deactivating compacted sponge iron comprising subjectingthe sponge iron, immediately upon its discharge into air, to the actionof-a stream of air to cool the sponge iron and prevent its temperaturefrom rising more than 400 F.

2. A method of deactivating compacted sponge iron comprising deliveringthe sponge iron into open air, permitting a slight initial oxidation ofthe sponge iron and then cooling the sponge iron in a stream of air toarrest said oxidation and prevent the temperature of the sponge ironfrom rising more than 400 F. above its temperature at the time of itsdelivery into open air.

3. A method of deactivating compacted sponge iron comprising breakingsaid sponge iron into pieces and subjecting said pieces to a tumblingaction while at the same time blowing cooling air over said pieces toprevent the temperature of said pieces from rising more than 400 F.during said tumbling action.

4. A method of deactivating compacted sponge iron comprising deliveringsaid sponge iron into open air and permitting an initial oxidation ofsaid sponge iron accompanied by a temperature rise of not more than 400F., and blowing a stream of cooling air on said sponge iron to arrestsaid oxidation and cause the temperature of the sponge iron to bereduced.

5. A method of deactivating sponge iron comprising compacting thefreshly reduced iron into strips in a new oxidizing atmosphere,discharging the compacted sponge iron into open air and immediatelysubjecting the sponge iron to the cooling action of a stream of airblown directly thereon, whereby oxidation of the surface of the spongeiron is arrested before the temperature of the sponge iron has risenmore than 400 F. above its temperature at the time of its discharge intoopen air.

-6. A method according to claim 1 wherein the compacted sponge iron isat a temperature of 100 F. to 400 F. upon its discharge into air.

7. A method according to claim 2 wherein the com- 3 4 pacted sponge ironis at a temperature of from 100 F. to References Cited in the file ofthis patent 400 F. at the time of its delivery into ope air. UNITEDSTATES PATENTS 8. A method accordmg to elazm 3 wherem the pleces1,695,041 Elman Dec 11, 1948 of compacted sponge iron are at atemperature of from 100 F. to 400 F. when they are first subjected tothe 5 2'501128 tumbling action.

Kerr Mar. 21, 1950

1. A METHOD OF DEACTIVATING COMPACTED SPONGE IRON COMPRISING SUBJECTINGTHE SPONGE IRON, IMMEDIATELY UPON ITS DISCHARGE INTO AIR, TO THE ACTIONOF A STREAM OF AIR TO COOL THE SPONGE IRON AND PREVENT ITS TEMPERATUREFROM RISING MORE THAN 400* F.